1. Field of the Invention
The invention relates in general to basketball backboards and other moldable, plastic parts of basketball goal assemblies and, more particularly, to basketball backboards and other parts of basketball goal assemblies formed of thermoplastic materials made in a compression molding process enabling use of an integrally molded graphics sheet.
2. Description of Related Art
Basketball backboards are currently made of a variety of materials and are commonly produced using a moldable plastic material. Compression molding has been a common method of producing basketball backboards and related parts of basketball goal assemblies for many years. Heretofore, compression molding of basketball backboards and related parts has been limited to thermoset materials, which is characterized by placement of a cold charge in a compression mold. Thermoset processed materials have certain drawbacks, including the fact that these materials are generally not recyclable other than as filler materials. In general, there are two basic types of compression molding processes which may be used for molding thermoplastics. The following description of these two processes outlines some of the difficulties that have prevented use of compression molded thermoplastics in the basketball goal assembly field.
The first type is a sheet molding process that involves placing a reinforcement, such as a glass mat, between sandwiching layers of a thermoplastic and heating the materials to produce a single sheet of material. The single sheet of material is then cut to the desired size and then reheated to molding temperature before being placed in a compression molding press. This process has the disadvantage of higher cost because of the apparatus required, the material handling costs incurred in making the sheet, handling and cutting the sheet, and the like. The material used to make the sheet is also subject to three thermodynamic cycles, a first cycle when the thermoplastic sheet is formed, a second cycle when the thermoplastic sheets and glass mat are molded together, and a third cycle when the resulting sheet is heated to molten temperature prior to molding the part.
The second form of thermoplastic compression is bulk molding compounds by producing a billet of molten material that is placed into a compression molding press which molds the molten material into a part. Effectively placing and distributing long reinforcing fibers in the billet has heretofore required complex machinery as discussed in detail in PCT International Publication Number WO 95/26823 having an International Publication Date of Oct. 12, 1995, the disclosure of which is incorporated herein by reference. Neither of these prior processes has been able to use post consumer recycled materials, which typically contain dissimilar, contaminated thermoplastics, without costly cleaning and processing that makes use of recycled thermoplastics impractical.
In addition, in recent years, it has become increasingly common to provide graphics on the front face of backboards for a variety of reasons, including aesthetic appeal to the consumer, product and source identification, etc. However, the only commercially acceptable methods of applying graphics have been silk-screening with inks or applying decals. Silk-screening is time consuming and the inks tend to fade after prolonged exposure to sunlight and the elements. Decals are also expensive and can peel off after time. An example of a prior art basketball backboard with silk-screened graphics is a backboard sold by a company known as "SureShot." The silk-screened SureShot backboard is 48 inches across and made of structurally foamed polystyrene molded in a multiple-port injection process. The backboard is molded in the natural color of polystyrene, which is a milky white color. The entire SureShot backboard is subsequently spray painted, both to seal the polystyrene and protect the backboard from ultraviolet radiation. Finally, graphics are silk-screened on the front face of the backboard.
To improve upon the graphics provided in basketball backboards, the assignee of this application has pioneered producing molded backboards with inmold graphics technology, which typically is accomplished by printing on a sheet or substrate using a full color printing process. This sheet is then placed in the mold and bonds/melts with base material during the molding operation and becomes a permanent "inmolded" graphics sheet. The advantage of this technology is the ability to print any image onto the sheet in one printing process (versus one silk-screen operation for each color) and the use of specially formulated inks that resist fading due to the sunlight and elements. This prior art inmold process was first introduced with polystyrene resin in a straight injection molding process.
Specifically, this first inmold process was used to produce a small backboard structure designed for youth sports, which was sold under the "Mini Jammer" name. The "Mini Jammer" backboard was formed by injecting styrene into a straight injection mold to form the styrene into the final desired shape of the backboard, which was small, i.e. less than 48 inches. The graphics display was printed on a styrene sheet laid by hand into the mold for forming the backboard. Alignment of the sheet was accomplished by aligning holes in the sheet on pins in the mold provided for producing the mounting holes in the backboard. Upon injecting styrene into the mold, the back portion of the graphics sheet melted to cause it to be integrally joined to the face of the backboard. As styrene is relatively easy to print on, its use in this prior art process was conducive to the production of backboards provided with sheets having graphics printed thereon.
In the parent application Ser. No. 08/190,914, an improvement of the prior inmold graphics process is disclosed that uses structural foam technology to mold backboards from polyolefin materials. The developments disclosed in this application greatly enhance the impact strength and structure (playability) of the backboard, thereby permitting the use of an inmold graphics sheet with larger backboards, such as 48 inches. In particular, this is accomplished by providing a basketball backboard formed of a structural foam plastic material, such as a polypropylene, molded in an injection molding operation. By molding the backboard using a structural foam material, the backboard is provided with an internal cellular structure and has a tough external skin, which provides good rebound characteristics. A printed graphics sheet formed of a material compatible with the backboard material, such as one formed of the same base resin material, is bonded to the backboard simultaneously with the molding operation of the backboard such that the graphics sheet is inmolded with the backboard structure. There is greater difficulty associated with printing on polyolefin materials than the prior art styrene material due to polyolefin-based materials being relatively non-porous and therefore not receptive to printing inks. To overcome this problem, the graphics sheet is corona treated prior to printing to produce pores in the sheet for receiving ink during printing.
The foregoing demonstrates that there is a need for a compression molding process for making basketball backboards and related basketball goal assembly parts from recyclable thermoplastic materials without requiring the extensive cleaning and processing that heretofore has made use of thermoplastics for these products impractical. There also is a need to further develop the inmold graphics process to permit its use in basketball backboards and other molded plastic parts of basketball goal assemblies made by compression molding thermoplastic resin materials.